The invention relates to exhaust mufflers for internal combustion engines of the kind comprising a closed chamber having an inlet pipe and an outlet pipe and containing means for absorbing noise in exhaust gases flowing into the chamber through the inlet pipe before the gases pass from the chamber through the outlet pipe.
As is well known, in mufflers of this type any improvement in the noise reducing properties of the muffler is usually accompanied by a reduction in the rate of flow of exhaust gases through the muffler, this reduction in rate of flow causing loss of power and efficiency of the engine and increase in fuel consumption.
International exhaust noise regulations are currently placing increasingly stringent limits on the noise output of motor vehicle exhausts, while at the same time there is an increasing demand for fuel economy. For the reason mentioned above, these requirements are to a certain extent conflicting and it is therefore an object of the invention to provide an exhaust muffler which effectively limits the noise output from the engine while at the same time maintaining a high flow rate of exhaust gases through the muffler.
Although it is desirable for the noise output from an engine exhaust to be kept low, there is also a requirement, particularly where the muffler is for use with engines in high performance vehicles, that the exhaust note which is produced should have a deep, powerful sound. It is therefore a further object of the invention to provide a muffler which may be constructed with a bias towards reducing noise in the high and midrange frequencies.